Production of metals



Dec. 1, 1959 Filed Oct. 16, 1957 y 3 Sheets-Sheet 1 MOLE FRACTION SALT .9 .a -.7 .e .5 .4 ,3 .2 .1 Ilillllll 0 ONE uouqo 1Q8Q HOO v l I .7 1ooo I C I -900 TWO LIQIUIDS souo SALT LJQUID METAL- FIG.1

INVENTORJ Edward G. Liv-(143w BY Non/ B12: L y

" Dec. 1, 1959 E. HELLIER ETAL 2,915,332

PRODUCTION OF METALS Filed 061.- 16, 1957 3 Sheets-Sheet 2 INVENTORS Edward G- Hz/lfcr BY Norman [haze -2y pow Lu QQYWGMCI,

E. s. HELLIER ETAL 2,915,382

PRODUCTION OF METALS Dec. 1, 1959 Filed 001.- 16, 1957 3 Sheets-Sheet 3 TiCl Na Zone Zone l4 l2 Zone i -13 "if 9" Zone Zone C C United States Pate PRODUCTION OF METALS Edward G. Hellier, Hingham, Norman Beecher, Concord,

and Paul L. Raymond, Natick, Mass, assignors to National Research Corporation, Cambridge, Mass, a corporation of Massachusetts Application October 16, 1957, Serial No. 690,566

4 Claims. (Cl. 75+63) This invention relates to the production of titanium. 7 It is a principal object of the instant invention to provide an improved process for the production of titanium.

Another object of the instant invention is .to provide an improved process for the separation of excess sodium, which is used as a reducing metal, from the product mass formed by the metallothermic reduction of a titanium chloride.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and the order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of .the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein;

Fig. -1 is a graph representing the solubility of sodium in sodium chloride and;

. Fig. 2 is a diagrammatic, schematic illustration of a preferred embodiment of the invention, and

Fig. 3 is a diagrammatic, schematic illustration of an- ;other preferred embodiment of the invention.

In the instant invention, chlorides of titanium metal are metallothermically reduced in a reactor with sodium metal to produce a molten reaction mixture comprised primarily of titanium metal, sodium chloride and excess sodium metal. Excess sodium metal is separated from the remainder of the product mixture by exploiting the dependency upon temperature of the solubility of sodium metal in sodium chloride. Specifically, the product mixture from the metallothermic reduction reaction which mixture contains molten sodium chloride and molten sodium metal is cooled to a temperature at which sodium metal has no appreciable solubility in sodium chloride but at which the mixture remains molten. Because the density of sodium metal (specific gravity .76 800 C.) is lower than that of sodium chloride (specific gravity 1.5 800 C.) the sodium metal tends to concentrate in the top portions of the mixture. In this way, substantially the entire quantity of sodium metal present is segregated in a layer in the upper portions of the mixture. The sodium chloride layer is then solidified in such a manner as to cause the surface portions of the layer to be the last to solidify. The sodium metal concentrated above the sodium chloride is then quickly and easily removed, thereby allowing the remaining mixture to be leached with a water solution without the attendant rapid temperature increases and large pressure rises together with danger of fire and explosion generally involved in such an operation.

It should be pointed out that if a molten mixture of sodium metal and sodium chloride is allowed to cool without any control of the cooling, a separation of the 2,915,382 Patente Dec. 1, 195.9

ice

sodium metal and the sodium chloride into distinct layers do ak Place .I th ns an el e. h sod um meta tends to concentrate on the surface of the mixture. How.- ever, as the sodium chloride layer cools further, and final.- ly solidifies, thermal fissures are formed in the mass of the solid chloride. The molten sodium metal quickly flows into these fissures, the end result being that the sodium metal is again lost in the interstices of the solidified sodium chloride.

In the instant invention, however, this problem is remedied by progressively solidifying the sodium chloride layer starting at the bottom thereof. In this way, he thermal fissures formed in the sodium chloride layer are formed progressively from the bottom of the mixture. This is greatly advantageous because fissures formed at the bottom of the sodium chloride layer fill with molten sodium chloride from above almost as quickly as they are formed. Of course, when finally the top layers of the sodium chloride layer are allowed to solidify, any fissures formed in the surface layer of the solified so.- dium chloride fill with molten sodium metal which be} cause of its relatively low melting point (97.5 C.) re.- mains molten for some time after the sodium chloride layer has solidified. However, since these surface fissures remain open at the top, and since the sodium metal remains molten for some time, the sodium metal can be easily removed, for example, by inverting .the reactor.

In a preferred embodiment of the invention, the reduction of the titanium metal chlorides with sodium metal is carried out in a reaction vessel which can be at least partially inverted. Following the completion of the metallothermic reaction between the titanium chlorides and the sodium metal, the molten mixture in the reaction vessel is allowed to cool until substantially the entire quantity of sodium metal present in the mixture is segregated in a layer at the top of the mixture. The sodium chloride layer is then caused to solidify,

.care being taken to cause the surface portions of the layer to be the last to solidify. When all of the sodium chloride (which contains the titanium metal) has solidified, the reaction vessel is inverted thereby causing the sodium metal, which has remained molten and which has concentrated on the surface of the reaction vessel, to drain off, while the solidified sodium chloride is left behind in the reaction vessel. The titanium metal product is subsequently separated from the sodium chloride by ordinary leaching procedures.

Re r n t h d a n s. the e s t ed in Fig. 1 a phase diagram illustrating the solubility of sodium in sodium chloride. In this drawing temperature is plotted against mole fraction of the salt. As can be seen, the solubility of sodium in sodium chloride is very low at the freezing point (800 C.) of sodium chloride. In Fig. 2, there is illustrated one type of apparatus showing a specific embodiment of the invention. Titanium tetrachloride and excess sodium metal are reacted at a temperature of between about 850-1000 C. in reactor 2 which is positioned within multi-zone furnace 4. The produced mixture 6 comprises principally titanium metal, excess sodium metal, and sodium chloride. When the reaction is substantially completed, reactor 2 is cooled to a temperature of about 810 C. At this temperature, the solubility of sodium metal in sodium chloride is less than about 1% (as shown in Fig. 1'). Consequently, since the solubility of sodium metal in sodium chloride decreases drastically and since sodium meta]v is lighter than sodium chloride, the sodium metal migrates upwardly, eventually concentrating on the surface 12 of the reaction mixture. The sodium chloride layer is then solidified in such a way as to cause the surface portions of the layer to be the last area to solidify.

This is preferably accomplished by adjusting the heating elements in zones A, B, and C so as to create strata of increasing temperatures in the reaction mixture starting at thebottomthereof where the temperature is maintained at about 7 C. and extending to the top thereof where the temperature is maintained slightly above about 800 C. The temperature at any level of the reaction mixture is measured by means of a thermocouple 7 in thermocouple well 8. Additional cooling of the contents of the lower portion of the reactor can be obtained if desired by allowing air to enter zone C by means of valve 10. Subsequently, the sodium metal 14 concentrated on surface 12,0f the mixture is removed quickly and easily by any well-known means such as by syphoning thereby allowing mixture 15 remaining in reactor 2 to be treated by ordinary leaching techniques.

Referring now to Fig. 3, there is illustrated a preferred means of separating the concentrated sodium metal 14 from the remaining mixture 16. Reactor 2 is removed from multi-zone furnace 4 after the sodium chloride layer has solidified but while the layer of concentrated sodium metal 14 is still molten (above about 975 C.). Reactor 2 is then partially inverted thereby causing the molten sodium metal 14 to drain ofl? surface 12 of the mixture. A collector means such as darn 17 positioned on wall 18 of reactor 2 collects the molten sodium metal. Reactor 2 is maintained in the inverted position until the molten sodium metal behind dam 17 has solidified whereupon the top 20 of reactor 2 is removed and the solidified sodium metal 22 recovered. The mixture 16 remaining in the reactor is then safely leached by ordinary leaching procedures.

Obviously many changes may be made in the above described process and apparatus without departing from the scope of the invention. Therefore, it is intended that all matter containedin theabove description and the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An improved process for producing titanium metal by metallothermically reducing in a reactor a chloride of titanium metal with sodium metal to produce a molten reaction mixture comprising titanium metal, excess sodium metal, and sodium chloride which process com prises cooling said reactionmixture below the temperature at which sodium metal has any appreciable solubility in sodium chloride thereby causing said sodium metal to come out of solution and to concentrate as a layer at the top of the molten sodium chloride, solidifying the sodium chloride so as to cause the upper surface portions thereof to be the last to solidify, removing the concentrated sodium metal, and subsequently separating the, titanium metal from the sodium chloride.

2. An improved process for producing titanium metal by metallothermically reducing in a reactor a chloride of titanium metal with sodium metal to produce a molten reaction mixture comprising titanium metal, excess sodium metal, and sodium chloride which process comprises cooling said reaction. mixture below the temperature at which sodium metal has any appreciable solubility in sodium chloride thereby causing said sodium metal to come out of solution and to concentrate as a layer at the top of the molten sodium chloride, solidifying the sodium chloride in the reactor so as to cause the upper surface portions thereof to be the last portions to solidify, maintaining the layer of concentrated sodium metal molten, removing said molten sodium metal, and subsequently separating the titanium metal from the solidified sodium chloride.

3. An improved process for producing titanium metal by metallothermically reducing in a reactor a chloride of titanium metal with sodium metal to produce a molten reaction mixture comprising titanium metal, excess sodium metal, and sodium chloride which process comprises cooling said reaction mixture below the temperature at which sodium metal has any appreciable solubility in sodium chloride thereby causing said sodium metal to come out of solution and to concentrate as a layer at the top of the molten sodium chloride, progressively solidifying the sodium chloride in the, reactor so as to cause the upper surface portions thereof to be the last portions to solidify while maintaining the layer of concentrated sodium metal molten, and subsequently inverting the reactor in order to cause said molten sodium metal to drain off.

4. An improved process for producing titanium metal by metallothermically reducing in a reactor a chloride of titanium metal with sodium metal to produce a molten mixture comprising titanium metal, sodium chloride and excess sodium metal, which process comprises cooling said reaction mixture to a temperature on the order of about 810 C. thereby causing the excess sodium metal to come out of solution and to concentrate as a layer at the top of the molten sodium chloride, progressively solidifying the sodium chloride so as to cause the upper surface portions thereof to be the last portions to solidify while maintaining the layer of concentrated sodium metal molten, and removing said molten sodium metal from said solidified sodium chloride.

References Cited in the file of this patent UNITED STATES PATENTS 2,621,120 Pedersen et al. Dec. 6, 1952 2,828,516 Black et al Apr. 1, 1958 

1. AN IMPROVED PROCESS FOR PRODUCING TITANIUM METAL BY METALLOTHERMICALLY REDUCING IN A REACTOR A CHLORIDE OF TITANIUM METAL WITH SODIUM METAL TO PRODUCE A MOLTEN REACTION MIXTURE COMPRISING TITANIUM METAL, EXCESS SODIUM METAL, AND SODIUM CHLORIDE WHICH PROCESS COMPRISES COOLING SAID REACTION MIXTURE BELOW THE TEMPERATURE AT WHICH SODIUM METAL HAS ANY APPRECIABLE SOLUBILITY IN SODIUM CHLORIDE THEREBY CAUSING SAID SODIUM METAL TO COME OUT OF SOLUTION AND TO CONCENTRATE AS A LAYER AT THE TOP OF THE MOLTEN SODIUM CHLORIDE, SOLIDIFYING THE SODIUM CHLORIDE SO AS TO CAUSE THE UPPER SURFACE PORTIONS THEREOF TO BE THE LAS TO SOLIDIGY, REMOVING 